Solution: Go through border control with blank phone/laptop and restore from backup later.
If most people erase their devices, it's a kind of giving up. Accepting data loss (hopefully temporarily, but not everything is stored in the cloud, e.g. SMS messages, at least in Android phones with the original texting app) is punative. And disproportionate. And resets are a PITA for non-technical people. As a work around to avoid being harassed, to me it proves we've lost the privacy fight.
Speaking of disproportionate...I think it’s disproportionate to surrender my phone to DHS/ICE for unwarranted inspection in order to enter the country.